1. Field of the Invention
The present invention relates to a drive gear, and more particularly to a hollow drive gear reduction mechanism.
2. Description of the Prior Art
FIG. 1 shows a conventional harmonic drive gear reduction 10 which comprises a wave generator 11, a flexible spline 12 sleeved onto the wave generator 11, and a rigid spline 13 sleeved onto the flexible spline 12. The wave generator 11 comprises an elliptical cam 111 and flexible bearing 112 sleeved on the elliptical cam 111. The elliptical cam 111 is connected to and driven to rotate by a power source. When the elliptical cam 111 rotates, it will push against and make the flexible bearing 112 and the flexible spline 12 deform, and as a result, the teeth at different parts of the deformed flexible spline 12 will be engaged with the teeth of corresponding part of the rigid spline 13, furthermore, the flexible spline 12 has less teeth than the rigid spline 13, so that a rotation speed reduction is achieved. However, this drive gear reduction is a solid structure, and almost provides no room for wiring.
Hence, another hollow drive gear reduction 20 was developed as shown in FIGS. 2 and 3, and comprises a hollow base 21, a support member 22 is pivotally disposed in the hollow base 21, and a reduction wheel 23 sleeved onto the support member 22. Then, an output member 24 is fixed to the support member 22 to output power. A drive power source 25 is non-axially inserted in the hollow base 21 with respect to the support member 22, the reduction wheel 23 and the output member 24 and engaged with the reduction wheel 23, so that drive power is transmitted from the drive power source 25 to the output member 24 via the support member 22 and the reduction wheel 23, and then outputted from the output member 24, so rotation reduction is achieved, and the hollow base 21 provides room for wiring. However, the drive power source 25 is inserted deeply into the hollow base 21 and engaged with the reduction wheel 23 in a non-axial manner, and non-axial arrangement would not only increase the size of the whole drive gear reduction mechanism, but also make assembly more difficult. Furthermore, since the drive power source 25 uses a small toothed drive wheel to engage with and drive the reduction wheel 23 which is much larger than the small toothed drive wheel, backlash will appear between the drive power source 25 and the reduction wheel 23, which consequently will cause motion loss, angular motion error, and vibration. Hence, using toothed wheel as a drive wheel requires high machining and assembling accuracy, and increases manufacturing cost.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.